My primary research interest is Astroparticle physics wherein I study issues at the interface of particle physics and cosmology. This includes study of early universe and the late time acceleration which is believed to be driven by dark energy.
At present I am working on theoretical and observational aspects of dark energy. Understanding dark energy has been the focus of a flurry of activity for more than a decade. This negative pressure component is required to drive the present day acceleration of the universe, a fact which is confirmed by various observations. Since dark energy is an unknown component of the universe, various models have been proposed to explain the acceleration of the universe. Given a large number of models: and the relative lack of understanding, it becomes important to constrain and if possible rule out various models using observations. A large amount of data and the quality of observations available makes this task possible. I work on obtaining constraints on the cosmological parameters, especially constraining present day value of dark energy and its variation with redshift.
On the theoretical front, I investigate how dark energy perturbations affect the formation of structures in the universe. Pure distance measurements are insufficient to distinguish between models with the same background evolution. Evolution of perturbations, on the other hand, depends on the details of the model. I am interested in studying whether the dark energy perturbations enhance or suppress dark matter perturbations and how the effect can be measured observationally.
- Evolution of perturbations in distinct classes of canonical scalar field models of dark energy, H.K. Jassal, Phys. Rev. D81, 083513 (2010).
- Understanding the origin of CMB constraints on Dark Energy, H. K. Jassal, J. S. Bagla, T. Padmanabhan, Mon. Not. Roy. Astron. Soc. 405, 2639 (2010)
- A comparison of perturbations in fluid and scalar field models of dark energy, H. K. Jassal, Phys. Rev. D81, 127301 (2009)
- Scalar Field Dark Energy Perturbations and their Scale Dependence, Sanil Unnikrishnan, H.K. Jassal, T.R. Seshadri, Phys. Rev. D78, 123504 (2008)
- WMAP constraints on low redshift evolution of dark energy, H. K. Jassal, J. S. Bagla, T. Padmanabhan, Mon. Not. Roy. Astron. Soc. 356, L11 (2005)